Human blood vessels often become occluded or completely blocked by plaque, thrombi, other deposits, emboli or other substances, which reduce the blood carrying capacity of the vessel. Should the blockage occur at a critical place in the circulatory system, serious and permanent injury, or even death, can occur. To prevent this, some form of medical intervention is usually performed when significant occlusion is detected.
A serious example of vascular occlusion is coronary artery disease, which is a common disorder in developed countries and is the leading cause of death in the United States. Damage to or malfunction of the heart is caused by narrowing or blockage of the coronary arteries that supply blood to the heart. The coronary arteries are first narrowed and may eventually be completely blocked by plaque (atherosclerosis), and the condition may further be complicated by the formation of thrombi (blood clots) on roughened surfaces of, or in eddy currents caused by the plaques. Myocardial infarction can result from coronary atherosclerosis, especially from an occlusive or near-occlusive thrombus overlying or adjacent to the atherosclerotic plaque, leading to ischemia and/or death of portions of the heart muscle. Thrombi and other particulates also can break away from arterial stenoses, and this debris can migrate downstream to cause distal embolization.
Various types of intervention techniques have been developed to facilitate the reduction or removal of a blockage in a blood vessel, allowing increased blood flow through the vessel. One technique for treating stenosis or occlusion of a blood vessel is balloon angioplasty wherein a balloon catheter is inserted into the narrowed or blocked area, and the balloon is inflated to expand the constricted area. Other types of interventions include atherectomy, deployment of stents, local infusion of specific medication, and bypass surgery. Each of these methods is not without the risk of embolism caused by the dislodgement of the blocking material, which may then move downstream.
Often, more than one interventional catheter is used during a procedure, such as to change the size of the balloon being used or to introduce additional devices into the system to aid with the procedure, including stent delivery catheters and aspiration catheters. In such situations, the catheters are generally inserted into the patient's cardiovascular system with the assistance of a guidewire. For example, a guidewire is introduced into the patient, steered through the tortuous pathways of the cardiovascular system, and positioned across an intended treatment location. Various catheters having a lumen adapted to receive the guidewire may then be introduced into and removed from the patient along the guidewire, thereby decreasing the time needed to complete a procedure.
Many techniques exist for preventing the release of thrombotic or embolic particles into the bloodstream during such a procedure. Common among these techniques is introduction of an occlusive device or a filter downstream of the treatment area to capture these embolic or thrombotic particles. The particles may then be removed from the vessel with the withdrawal of the occlusive or filtering device. In another common technique, the particles may be removed by an aspiration catheter prior to the withdrawal of these devices. Aspiration catheters have also been found useful in removing thrombus prior to crossing underlying atherosclerotic plaque with guidewires and/or treatment catheters. Such preliminary removal of thrombus makes it easier to cross the stenosis and less likely to release thrombo-embolic particles into the bloodstream during the procedure.
An aspiration catheter may be designed such that a guidewire is contained within the aspiration lumen as the catheter is advanced there over, or the aspiration catheter may include a dedicated guidewire lumen extending along substantially the entire length of the aspiration catheter such that the guidewire is disposed therein as the catheter is advanced through a body lumen. Such dual-lumen catheters having an aspiration lumen and a guidewire lumen may be constructed in a variety of ways including relatively simple profile extrusions, more complex assemblies of different tubular components, and combinations of these two methods.
Dual-lumen profile extrusions can have parallel round lumens surrounded by relatively uniform walls, resulting in a non-circular, generally figure-eight shaped transverse cross section. Alternatively, if a circular outer profile is desired, then dual-lumen profile extrusions can have parallel round lumens with non-uniform wall thicknesses or various other combinations of lumens having unequal sizes and non-round cross-sectional shapes such as D-shapes or crescent-shapes, as will be understood by one of skill in the field of cardiovascular catheters.
One of the important features of aspiration catheters is the ability to rapidly and efficiently aspirate even large embolic particles without the need to first break them into smaller sub-particles. This advantage is achieved, at least in part, by providing the catheter with an aspiration lumen having as large a cross sectional area as possible, given overall size constraints of the catheter design. In embodiments having an aspiration lumen that is crescent shaped or has another non-round shape, a relatively large cross-sectional area is preferably maintained to achieve rapid and efficient aspiration.
Aspiration catheters may also be of the so-called single operator or rapid exchange type. A rapid exchange aspiration catheter typically includes a tubular catheter shaft with an aspiration lumen extending the entire length thereof and a substantially shorter guidewire lumen extending along a distal portion of the catheter. As such, the guidewire is located outside of the aspiration catheter except for a short guidewire segment that extends within the guidewire lumen. Advantageously, a clinician is able to control both ends of the guidewire while the aspiration catheter is loaded or exchanged onto the guidewire, which may be already indwelling in the patient. The aspiration catheter is then advanced through the patient's vasculature with only a distal portion of the catheter riding on the guidewire.
Several types of aspiration catheters are disclosed in U.S. Patent Application Publication 2007/0106211 to Provost-Tine et al., which is incorporated by reference herein in its entirety. One of the aspiration catheters in the '211 publication is a rapid-exchange configuration, illustrated as FIG. 1 of the present application. FIG. 1 illustrates an aspiration catheter 20 suited for use in the treatment and removal of occlusions in blood vessels. Catheter 20 has a fitting 27 mounted at the proximal end in fluid communication with a proximal aspiration port 23. Catheter 20 includes an elongate tubular body 21 having a distal tip 26. Distal tip 26 can include a radiopaque marker (not shown) to aid in fluoroscopically locating tip 26 during insertion into the patient, and tip 26 is preferably soft to prevent damage to the patient's vasculature. Elongate tubular body 21 includes an aspiration tube 31 extending from fitting 27 to a location at or adjacent the distal end of tubular body 21. Aspiration tube 31 includes a tubular wall that defines an open aspiration lumen 12 (shown in FIG. 2), which extends the full length of tube 31. Aspiration lumen 12 fluidly connects aspiration port 23 disposed at or adjacent the proximal end of tubular body 21 with a distal fluid port 24 disposed at or adjacent the distal end of tubular body 21. A source (not shown) of partial vacuum or “negative pressure” may be connected to the luer adaptor of fitting 27 to aspirate blood and particulates through aspiration lumen 12 of catheter 20.
Catheter 20 further includes a dual lumen section 41 that is substantially shorter than the full length of catheter 20. Dual lumen section 41 includes a guidewire tube 51 that defines an open guidewire lumen 15 (shown in FIG. 2) sized and shaped to slidingly accept a medical guidewire therethrough. Guidewire tube 51 extends from an open proximal end 290 to an open distal end 29, alongside a distal portion of aspiration tube 31 such that aspiration lumen 12 and guidewire lumen 15 are in a parallel or side-by-side configuration. Dual lumen section 41 thus extends proximally from second fluid port 24 disposed at the distal end of aspiration tube 31 to open proximal end 290 of guidewire tube 51.
FIG. 2 is an enlarged cross-sectional view of open proximal end 290 of guidewire tube 51, showing a guidewire 50 extending through guidewire lumen 15. As shown in FIG. 2, open proximal end 290, which may also be referred to as a proximal guidewire port, of guidewire tube 51 is attached to the outer surface of aspiration tube 31. When the proximal guidewire port is attached to the catheter shaft in this manner, forces applied in a transverse direction to separate the guidewire from the catheter may cause the guidewire to tear the wall of guidewire tube 51, starting from open proximal end 290. There is therefore a need for an improved aspiration catheter that avoids the above-described problem of the guidewire tearing the guidewire shaft.